3.3.1. Calculation of Carbon Emissions

(1) To determine the carbon emissions produced from construction land, this study mainly considered the carbon emissions produced through energy consumption by the industrial and mining enterprises and the transportation industry. In accordance with the reference method proposed in the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, the carbon emissions from construction land were calculated as follows:

$$\text{Ch} = \sum\_{i} \text{Qh}\_{i} \cdot \text{NCV}\_{i} \cdot \text{CC}\_{i} \cdot \text{COF}\_{i} \cdot \frac{44}{12} \cdot \frac{1}{1000} = \sum\_{i} \text{SC}\_{i} \cdot F\_{i} \tag{1}$$

$$\mathbb{S}\mathbb{C}\_{i} = \mathbb{Q}h\_{i} \cdot \mathbb{C}\mathbb{S}\_{i} \tag{2}$$

where *SCi* represents the quantity of standard coal converted from every kind of energy source (*kgce*); *Qhi* represents the consumption of every kind of energy (*kg*); and *CSi* represents the standard coal conversion coefficient from each energy source (*kgce*/*kg*),

$$F\_i = CC\_i \cdot CF\_i \cdot \frac{44}{12} \cdot \frac{1}{1000} \cdot 29.3076\tag{3}$$

where *Fi* represents the standard coal emission factor (*kgCO*2/*kgce*); *CCi* represents the carbon content of fossil energy (*kC*/*G J*); *COFi* represents the carbon oxidation factor; <sup>44</sup> <sup>12</sup> is the carbon content per molecule CO2(*kgCO*2/*kg*); <sup>1</sup> <sup>1000</sup> is the unit conversion factor; and 29.3076 (*M J*/*kgce*) is the low calorific value of standard coal per kg according to the general rules of the GB/T2589-1990 comprehensive energy consumption calculation.

For cultivated land, because carbon emissions are produced over a long time scale, changes in crop yield have little impact on carbon absorption and emissions by the ecosystem [16]. Thus, only human-induced carbon emissions from agricultural activities were considered. This included carbon emissions caused by the powering of agricultural machinery, through the use of fertilizers and pesticides, and through agricultural irrigation. In accordance with Tristram O West [17] and the Institute of Agricultural Resources and Eco-Environment Performance of Nanjing University, the carbon emissions produced from cultivated land were calculated as follows:

$$E\_b = \mathcal{U}\_{fN} \cdot A\_N + \mathcal{U}\_{fP} \cdot A\_P + \mathcal{U}\_{fK} \cdot A\_K + \mathcal{U}\_m \cdot B + \mathcal{U}\_p \cdot \mathbb{C} + \mathcal{U}\_a \cdot D + \mathcal{S}\_i \cdot E + \mathcal{S} \cdot F \tag{4}$$

where *Uf N* represents the consumption of nitrogen fertilizer; *Uf P* represents the consumption of phosphate fertilizer; *Uf K* represents the consumption of potassium fertilizer; *AN* = 857.54 *kgC Mg* , *AP* <sup>=</sup> 165.09 *kgC Mg* and *AK* = 120.28 *kgC*/*Mg* are conversion coefficients of types of fertilizer; *Um* represents the total power needed for agricultural machinery; *Up* represents the consumption of pesticides; *Ua* represents the consumption of agricultural film; *Ua* represents the area of agricultural irrigation; *S* represents the area of crop planting; and *B* = 0.18 *kgC*/*kwh*, *C* = 4907.25 *kg*/*Mg*, *D* = 5.18 *kg*/*kg*, *E* = 266.48 *kgC*/*ha*, *F* = 16.47 *kgC*/*ha* are conversion coefficients.

(2) Carbon emissions from other land-use types were calculated using the following direct carbon emission coefficient method:

$$C\_i = S\_i \times k\_i \tag{5}$$

where *Ci* represents the carbon emissions produced from different land-use types; *Si* represents the area taken up by each land-use type; and *ki* represents the carbon emission coefficient of each land-use type.

In terms of the carbon emission coefficients of woodland and grassland, based on the fact that the main vegetation type present in Jinhua is evergreen coniferous forest mixed with a small amount of evergreen broad-leaved forest [18], we referred to the relational expression *CSE* = *carbon sink*/*NPP* from the research results of Fang et al. [19] and Lai [3] and selected −0.374 tC/ha·a as the carbon emission coefficient for woodland in Jinhua and −0.021 t/ha·a as the carbon emission coefficient of grassland.

Regarding the water carbon emission coefficient, according to the research results of Duan et al. [20], the carbon sink capacity of the lake wetland in the Eastern Lake Area where Jinhua is located is −0.567 tC/ha·a. According to the research results of Lai Li, the carbon sink capacity of the tidal flat is −0.236 tC/ha·a. The secondary classification of waters in the LUCC classification system includes lakes, rivers, canals, reservoirs, ponds, tidal flats, and beaches. For comprehensive consideration of the carbon sink capacity of different types of water and the average carbon sink capacity of waters across the country, the carbon sink coefficient of the study was taken as −0.28 tC/ha·a [21].

Regarding the carbon emission coefficient of unused land, unused land includes sandy land, Gobi, saline-alkali land, marshland, bare land, and bare rock land. Among these, the carbon emissions are low except for swamps, which have a strong carbon sink capacity. In accordance with the research results of Lai [3], the carbon sink coefficient was taken as −0.005 tC/ha·a.
